Combine the beef, onion, oil, chili powder and garam marsala. Shape into balls. Set aside. Heat the remaining oil in a large saucepan and add onion and chili powder. Cook until softened – about 5 minutes. Add coconut milk, peanut butter and hot water. Bring to a boil. Reduce heat to simmer and stir in peanuts. Add meatballs and cook for 15 to 20 minutes until cooked through.